Sign in

What is a Dictionary Attack?

Nishit Agarwal
What is a Dictionary Attack?

If you're interested in learning how to break encryption or authentication systems, you may want to learn about dictionary attacks, which are attacks that use just the most probable decryption keys or passphrases to attempt to break them, frequently utilizing lists of previous security breaches as a guide.

This is a dictionary attack against a cryptosystem or authentication system’s algorithm.

Dictionary attacks aim to decrypt or acquire access by spraying a library of phrases or values. Dictionary words or numerical sequences may be utilized for automatic insertion into the target, although less random input is becoming increasingly prevalent (e.g. usernames and passwords from a prior data breach).

A cyber security course can be helpful to understand this subject in a better way. Dictionary attacks are made simpler by poor password hygiene such as upgrading passwords with sequential numbers, symbols, or characters. Passwords and other common secrets enable these assaults, which result in account takeover (ATO) and financial fraud.

Passwords may be hacked if they are simply "updated" by adding a new number or special character. A dictionary attack may readily break the user's addition of these characters, as such an attack can cycle through millions of permutations in a short period of time," we presume hackers already know your password from earlier breaches.


The idea of a dictionary attack is to test every possible combination of characters in a predetermined list. The term dictionary attack refers to assaults that employ words from a dictionary; nevertheless, there are already databases of hundreds of millions of passwords acquired from previous data breaches on the open Internet. Cracking software may also utilize such lists to generate common modifications, such as replacing digits for similar-looking characters. Only the most probable outcomes are considered in a dictionary assault. It is typical for dictionary attacks to succeed because many individuals choose to select short passwords that are conventional words, popular passwords or variations derived, for example, by attaching a digit or punctuation character. Many typical password-creation methods are covered by the provided lists, which are paired with cracking software pattern generation. Using a password management tool or manually inputting a password is the safest method for creating a lengthy password (15 letters or more) or a multiword passphrase.

Pre-Computed Dictionary Attack/Rainbow Table Attack

Pre-compiling a list of dictionary hashes and storing them in a database with the hash as the key allows for a time-space tradeoff. Preparation time is long, but the assault itself may be carried out more quickly as a result. Due to the cheap cost of disk storage, the storage needs for pre-computed tables have decreased significantly. When a large number of passwords have to be cracked, pre-computed dictionary attacks are most successful. Creating a pre-computed dictionary is a one-time process and once it is accomplished, password hashes may be quickly matched to their associated passwords at any given moment. The usage of rainbow tables, a more advanced method, reduces storage needs while increasing lookup times marginally. An example of an authentication system that has been breached by such an attack is the LM hash.

If the number of potential salt values is high enough, precomputed dictionary assaults, or "rainbow table attacks," may be prevented by using salt, a method that causes the hash dictionary to be recomputed for each password requested, rendering precomputation infeasible.

There are many cities in India which offer different cyber security courses like cyber security course in Hyderabad.

What’s the Difference Between Dictionary and Brute-Force Attacks?

Dictionary attacks, unlike brute-force assaults, only employ a restricted number of pre-selected words and phrases to get past authentication measures. While a dictionary attack takes less time and resources to perform, it reduces the chances that a complex password will be guessed successfully. It's common for an attacker to build a password dictionary based on a target's passwords, adds Heiland. London Widgets, for example, would be on the list of predetermined targets if it was a London-based company that was under assault, thus phrases like "Westminster," "ChelseaFC1990," "SouthBank2020," and "CityOfLondon2020" would be included in the list of words that may be used to attack the company. For example, replacing "a" with "@" or adding digits to passwords are typical modifications. In certain cases, the threat actor may steal personal data, financial information, intellectual property, or assault an organization. The best cyber security courses can help you to enhance your knowledge.

Nishit Agarwal
Zupyak is the world’s largest content marketing community, with over 400 000 members and 3 million articles. Explore and get your content discovered.
Read more